Conversion of hydrocarbons



Patented Feb. 11, 1947 UNITED STATES 2,415,477 CUNVERSION' F HYDRGCAREON S Hiilis 0. Folkins, Skokie, and Carlisle M. Thacher, Highland Park, Ill., assignors to The Pure 0111 Company, Chicago, Ill, a corporation of Ohio No Drawing. Application December 26, 1942,

Serial No. 470,304

2 For the purpose of this invention organic compounds are those having both carbon and hydrogen in the molecule.

We have found that when sulfur, hydrogen sulhydrocarbons. 5 fide and/or organic sulfur compounds are mixed An object of the invention is to convert higher with hydrocarbons undergoing conversion in an boiling hydrocarbons into lower boiling hydroamount of 3 molal per cent or less, a marked accarbons. v celeration in the rate of cracking occurs at tem- Another object of the invention is to provide a peratures above 375 C. Sensitizers, in accordmethod of accelerating the rate of conversion ance with our invention, are effective at sub-atof higher boiling into lower boiling hydrocarbons, mospheric, atmospheric and super-atmospheric A still further object of the invention is to propressure. vide a method for preparing unsaturated hydro- In order to demonstrate the effectiveness of carbons from saturated hydrocarbons. various compounds falling within the scope of A further object of the invention is to accelour invention, a number of tests were made in erate the cracking of saturated to unsaturated both a Pyrex reaction vessel and in a stainless hydrocarbong steel reaction. vessel. The results of these tests Still another object of the invention is to proare set forth in Tables I, II and III. In the vide a method of accelerating cracking of hydrogreat majority of tests normal butane was used carbons under known thermal conditions and in as the charging aterial. Some of the tests were present types of cracking apparatus. conducted with pentane as the charging stock. Other objects and advantages inherent in the The tests were carried out by heating the reaction invention will become apparent from the followvessel to reaction temperature (either 500 or ing description. 525 (3.), evacuating it, injecting into the evac- We have discovered that thermal conversion of uated vessel sufficient butane (or pentane), conhydrocarbons into lower boiling hydrocarbons taining the desired amount ofv sensitizer, to proand/or into unsaturated hydrocarbons can be acduce the desired n t al pressure s y a o t 1 celerated by introducing into the hydrocarbons atmosphere), allowing the reactionv to proceed undergoing conversion small amount of ulfur, until a pressure increase Of 25% over the initial hydrogen sulfide, and/or organic sulfur compressure was obtained, and then rapidly removpounds, preferably mercaptans, sulfides, disulfides 1 r cti n gases for an y The time reand other alkyl sulfur compounds. quired for an increase inpressure of 5, 12.5 and The particular compound or compounds select- 25 D 66m Was de A umber of blank ed as sensitizers should preferably be in the same runs i which 110 n t Zer Was used were made phase (liquid or vapor) as the charging stock in order to obtain'a comparison with the sensiat the temperature of reaction. As examples of tized runs. In the last column of the tables the sulfur compounds, which we have found useful, sensitization factor is the quotient of the time may be mentioned methyl, ethyl, n-propyl, is0- required for 25 per cent pressure increase for a propyl, n-butyl, iso-butyl, tertiary butyl, n-amyl non-sensitized run divided by the time required and iso-amyl mercaptans;methy1, ethyl, n-propyl, 40 for the same pressure increase in a sensitized allyl, methyl ethyl, methyl n-butyl and ethyl run. In Table I the tests were all carried out at n-butyl sulfides; and methyl and ethyl disulfides. a temperature of 525 C.

TABLE I 'Time in minutes Sensitizer required for presgg ggi' Charg sure increase offor 25% pressure Compound Per cent. 5% 12.5% 25% Increase 474248766313731 LL3 2 LL1 L1 L2 LLL Sensitization factor for 25% pressure increase Sensitization factor for 25% pressure increase 653263321227 0 0 0 0 fiw00 0 0 0 0 0 464984089969 321 2 1 22222fl222fl22 Run No.

27505 wmwwmm w .99773 0 .7 .7040824 141041112 11 1 11 TABLE III minutes minutes Gas analyses by volume IGS.

Time

required for pressure increase of- Time required for pressure increase of- 7-D50280 m69nl5-DO7 4. 2 &. 1 2 3 2 Percent 5% 12.5% 25% Percent .ILLLLLLL TABLE II TABLE I-Continued Sensitizer Compound Tet-CalIeSfiII do N-Cdia Sensitizer Compound (CH3)2S- Per cent Per cent Percent Percent OnHzn Charge Charge Per cent acid constituents Mixed mercaptans extracted from sour gasoline with aqueous caustic soda solution and stripped from the caustic soda with steam.

Run

332 N-C Hm 6.60 24.90

Run

310 do do 311..." do do 314.--" do do 271 N-C3H7SH Iso-C3H SH '308... do CH 1 Initial pressure slightly above atmospheric.

Run N0.

5. TABLE ln continued glf feazhilfides appear to have the greatest sensltizing G s analyses by vl'wme The runs tabulated in Table II were all D formed at 500 C. and had an initial pressure Percent 5 ofapproximately 400 min. with the exception of 36E 31 5 8 li i l e s those runs marked with an asterisk.

- Table III is a tabulation of the gas analyses by volume per cent of the gases produced in the runs tabulated in Tables I and II. The gas 10 analyses demonstrate that the composition of the gas produced in the cracking operation is fairly uniform, regardless of whether or not a sensitizer is used. The analyses also show that a considerable portion of the butane and pentane charged in the various runs was converted to unsaturated hydrocarbons and that very little hydrogen was produced in these runs, thereby demonstrating that the cracking took place between the carbon bonds rather than between carbon and hydrogen.

In order to demonstrate the efdcacy of sensitizers in accordance with our invention, when used in a continuous type process, a series of runs were made using Stoddards solvent as a charging stock in a flow apparatus. The Stoddards solvent had an A. P. I. gravity of 48.1, an initial boiling point of 395, and an end point of 390. The total sulfur content was .03 and the solvent contained no mercaptan sulfur. The results of these runs are recorded in Tabl IV. In making these runs the Stoddards solvent was preheated in a stainless steel tube of diameter and was then charged to a stainless steel reactor having a diameter of 3" and a length of 9 A". The temperatures of the preheater and reactor were maintained by an external electric heating element.

Runs 415 and 420 are blank runs. Runs 416 and 423 were carried out with hydrogen sulfide as the sensitizer. Run 425 was carried out with Although mercaptans, sulfides, disulfides and methyl sulfide as the sensitizer, The sensitizer hydrogen sulfide all generally accelerated the rate was added to the Stoddards solvent before it was of cracking of normal butane, as shown in Table I, charged to the preheater coil.

TABLE IV Run No 415 416 420 423 425 Reactor:

Top 501 501 475 476 501 Middle. 499 499 476 474 495 Temp, 0.: Bottom. 501 501 475 475 502 Preheater: Temp., 0.- 325 330 301 300 329 Pres. p. s. i. gauge. 500 502 500 500 500 Gal/hr. charged... 1 000 995 0.252 0.25 Wt. per cent sensitizer 0 142 H25 0 122 HES 0 47 Megs Liquid product per gal. charge (lbs) 6. 31 5 6. 26 6.2 Cu. ft. gas pergal. charge. 2.044 3 088 3.038 3. 508 2 749 Wt. per cent liquid prod 96. 9 96 2 96. 4 95. 96 7 Wt. per cent gas. prod 3.1 3 8 3. 6 4. 3 3 3 A. P. I. gravity of liquid 49. 4 49.7 49.2 49. 3 49 1 A. P. I. distillation of liqu B. 132 120 132 128 128 57 243 186 217 197 224 10 297 264 280 256 285 20% 320 310 315 305 315 7 331 322 330 326 331 40% 338 334 337 337 337 50% 344 342 344 345 343 349 347 351 352 349 355 354 357 357 355 362 362 365 366 361 374 375 378 380 2 395 398 394 404 389 E. P 424 437 445 454 428 Per cent recovered 97.0 97 0 98.0 97. 8 97. 5 Per cent residue 0. 0 8 1.0 1. 5 1. 1 Per cent loss 2. 2 2. 2 1.0 0. 7 1. 4 A. S. T. M. octane No 42. 2 43. 6 .49. 0 51.0 47.1 Bromine No 13. 0 17. 2 16. 3 19. 1 14.0 Sulfur compounds in liquid:

Per cent H 0. 010 0.005 None Per cent S as RSH 0.007 0.009 0. 019 Sulfurhcompounds in liquid after caustic soda was Per cent EZS None None Per cent S as RSEL 0. 002 .00 0. 005 Per cent free S None None Per cent S as RQSL. 0 001 None Per cent as RzS..- 0 007 0.056 Percent res. S 0. 009 0.008

From the results tabulated in Table IV it will be seen that sensitizer produced a liquid product which had a lower initial boiling point and a higher octane number than the product prepared without a, sensitizer, thereby definitely showing that higher cracking took place with the sensitizer in the same period of time than without the sensitizer. the greater extent of cracking in the sensitized runs is the bromine number showing a larger proportion of unsaturates in the distillate made in the sensitized runs than in the non-sensitized runs.

The analyses of the liquid product for sulfur compound indicat that by a simple aqueous caustic soda wash of the distillate the amount of sulfur compounds in the distillate can be reduced to a point where they are unobjectionable.

The invention is applicable to cracking of both low boiling and high boiling hydrocarbons within the range of 375 C. to approximately 709 C. The sensitizers are effective in very small amounts and when cracking gasoline or higher boiling hydrocarbons, should be used in amounts below 1 per cent by weight of the charge since larger amounts not only cause corrosion dificulties but deleteriously afiect the quality or the product. Good results are obtained by using from 0.25 to '1 molal per cent of the sensitizer.

The sensitizer may be added to the hydrocarbons under going cracking prior to charging the latter to the heating zone or may be injected directly into the reaction zone either alone or in admixture with a small amount of solvent.

The invention is useful in connection with conventional thermal cracking operations to accelerate the rate of cracking or maybe used in connection with catalytic cracking operations of the A further indication of stationary or moving bed catalyst type, or in conjunction with vapor suspended solid catalyst type of operation, in which solid, comminuted catalytic clays or synthetic alumina-silica or other solid catalysts are used.

What is claimed is: p The method of cracking butane to lower boiling unsaturated hydrocarbons which comprises subjecting it to temperatures above 375 C. in the presence of a small amount of ethyl sulfide.

H. O. FOLKINS. CARLISLE M. THACKER.

REFERENCES CITED Thei'ollowing references are of record in the file of this patent:

UNI'IED STATES PATENTS Number Name Date 1,221,698 Day Apr. 3, 1917 2,1638% Groll Aug. 8, 1939 2,268,994 Russell Dec. 30, 1911 1,925,421 Peski Sept. 5, 1933 2,232,999 Gohr Feb. 25, 1941 2,115,336 Krauch et a1 Apr. 26, 1938 OTHER REFERENCES A. P. C. Application of Woog, Ser. No. 330,613, Published May 18, 1943. 

